POJ 2420 A Star not a Tree? (模拟退火)

#include <iostream>
#include <cstdio>
#include <string>
#include <cstring>
#include <stdlib.h>
#include <math.h>
#include <ctype.h>
#include <queue>
#include <map>
#include <set>
#include <algorithm>

using namespace std;
#define LL __int64
const int INF=0x3f3f3f3f;
int n;
struct point
{
int x, y;
}dian[200];
double dist(point a, point b)
{
return sqrt((a.x-b.x)*(a.x-b.x)*1.0+(a.y-b.y)*(a.y-b.y));
}
double juhe(point x)
{
int i;
double z=0;
for(i=0;i<n;i++)
{
z+=dist(x,dian[i]);
}
return z;
}
int main()
{
int i, j, flag, step;
point st, ed;
scanf("%d",&n);
for(i=0;i<n;i++)
{
scanf("%d%d",&dian[i].x,&dian[i].y);
}
step=100;
st.x=0;st.y=0;
double d=juhe(st), s;
while(step>0.2)
{
flag=1;
while(flag)
{
flag=0;
point now;
now.x=st.x+step;
now.y=st.y;
s=juhe(now);
if(d>s)
{
flag=1;
d=s;
ed=now;
}
now.x=st.x-step;
now.y=st.y;
s=juhe(now);
if(d>s)
{
flag=1;
d=s;
ed=now;
}
now.x=st.x;
now.y=st.y+step;
s=juhe(now);
if(d>s)
{
flag=1;
d=s;
ed=now;
}
now.x=st.x;
now.y=st.y-step;
s=juhe(now);
if(d>s)
{
flag=1;
d=s;
ed=now;
}
if(flag)
st=ed;
}
step/=2.0;
}
printf("%.0f\n",d);
return 0;
}